Few studies have examined differences in the guilty plea decisions of youth and adults. In interviews with 64 youth (X = 15.9, SD = 1.2) and 56 adults (X = 38.5, SD = 11.5) who pleaded guilty to felonies in New York City, we found important differences between the youths and adults in their understanding of the plea process, the factors they considered when making decisions, and their rationales for their decisions. Youth were less likely to recognize that a guilty plea resulted in a criminal record and to understand the trial process, and they reported having considered fewer potential outcomes in their decision making than adults. Like adults, youth overwhelmingly reported pleading guilty for reduced charges or penalties, but were substantially less likely than adults to understand the nature of the rights they were waiving. Our findings raise the question of whether the assumption of competence for youth is reasonable, and whether steps to assess youth understanding and decisional competence should be taken before youth are allowed to enter into plea agreements. (PsycINFO Database Record (c) 2019 APA, all rights reserved).